1. Field of the Invention
The present invention relates to a polycrystalline silicon manufacturing apparatus which manufactures a polycrystalline silicon rod by depositing polycrystalline silicon on a surface of a heated silicon seed rod.
Priority is claimed on Japanese Patent Application No. 2008-084308, filed Mar. 27, 2008, the content of which is incorporated herein by reference.
2. Description of the Related Art
Conventionally, as this kind of polycrystalline silicon manufacturing apparatus, a polycrystalline silicon manufacturing apparatus using the Siemens method is known. In the polycrystalline silicon manufacturing apparatus using the Siemens method, plural seeds made of silicon are arranged in a hermetic reaction furnace and are heated, raw gas composed of a mixed gas of chlorosilane and hydrogen is supplied to the reaction furnace to contact with the heated silicon seed rods, and then deposit polycrystalline silicon on surfaces thereof by means of hydrogen reduction and thermal decomposing of the raw gas.
In the polycrystalline silicon manufacturing apparatus, the silicon seed rod serving as a seed is uprightly stood on an electrode disposed in the bottom of the reaction furnace, a current is supplied from the electrode to the silicon seed rod so as to heat the silicon seed rod by means of a resistance thereof, and then the raw gas ejected from the lower side contacts with the surface of the silicon seed rod so as to form a polycrystalline silicon rod. At this time, plural electrodes holding the silicon seed rods are installed and distributed in substantially the whole area of the bottom surface of the reaction furnace, and each electrode is surrounded by annular insulating materials in the perforation holes in the bottom plate portion of the reaction furnace as disclosed in Japanese Patent Application Laid-Open No. 2007-107030.
Incidentally, in the above-described polycrystalline silicon manufacturing apparatus, it is desirable to install the silicon seed rods in the reaction furnace in high density in order to improve productivity. However, in order to install more silicon seed rods in the reaction furnace, it is necessary to form more perforation holes in the bottom plate portion. As the number of the perforation holes increases, the rigidity of the bottom plate portion decreases, and the bottom plate portion is easily deformed. Additionally, each electrode is connected to a current-supply power source cable or a cooling pipe formed inside the electrode. Accordingly, when more electrodes are installed in the reaction furnace, many cables or pipes are densely provided below the reaction furnace, thereby causing a problem in that the maintenance workability deteriorates.